High genetic diversity at the inter-/intra-host level of Cherry leaf roll virus population associated with the birch leaf-roll disease in Fennoscandia

ABSTRACT

A viral epidemic associated with the Cherry leaf roll virus (CLRV) has emerged in Betula species in Fennoscandia, exhibiting quick and effective spread during the last 15 years. A population genetics approach is chosen in order to characterise the virus diversity and the sources of genetic variation aiming to investigate the epidemiology of the pathogen. In a CLRV population from Rovaniemi urban parks and a population that occurred after infecting young Betula seedlings with scions from the original Finnish trees, the genetic diversity is found to be remarkably high, mixed infections by CLRV variants from different phylogenetic groups are detected in single trees, while recombination is evidenced to occur. The estimated genetic variability is high and the CLRV haplotypes detected exhibit clear clustering and belong to different phylogenetic groups. The structure of the viral population reveals a pathogen with high evolutionary potential assumed to carry on its effective spread.

KEYWORDS:

• Viral pathogens
• mixed infection
• population diversity
• virus haplotypes
• evolutionary potential

Acknowledgements

The project was funded by the Deutsche Forschungsgemeinschaft [grant number BU890/15-1]. Matthias Breuhahn provided some of the raw data used in this study during his Bachelor study. The authors are thankful to Dr Celeste Linde for the valuable discussion regarding the population genetic analysis.